1-28
have less loading effect on circuits, a high-sensitivity meter will provide a more accurate voltage
measurement.
To determine the sensitivity of a meter movement, you need only to divide 1 by the amount of
current needed to cause full-scale deflection of the meter movement. The manufacturer usually marks
meter movements with the amount of current needed for full-scale deflection and the resistance of the
meter. With these figures, you can calculate the sensitivity
and the full-scale voltage reading full-scale current (full-scale current resistance).
)RU H[DPSOH LI D PHWHU KDV D IXOO VFDOH FXUUHQW RI A and a resistance of 960
W, the sensitivity
could be calculated as:
The full-scale voltage reading would be calculated as:
Full-scale voltage reading = full-scale current resistance
)XOO VFDOH YROWDJH UHDGLQJ $
960W
Full-scale voltage reading = 48mV
RANGES
Table 1-1 shows the figures for most meter movements in use today.
CURRENT TO
DEFLECT FULL
SCALE
RESISTANCE
SENSITIVITY
VOLTAGE FULL
SCALE
1mA
N 92/7
.1 V
$
N 92/7
.048 V
$
N 92/7
.029 V
Table 1-1.—Meter Movement Characteristics
Notice that the meter movements shown in table 1-1 will indicate .029 volts to .I volt at full scale,
and the sensitivity ranges from 1000 ohms per volt to 200,000 ohms per volt. The higher sensitivity
